TUMOR AND IMMUNO-METABOLISM BASED LACTATE TRANSPORTER INHIBITOR FOR METASTATIC MELANOMA Abstract Immunotherapy area for cancer is rapidly expanding with the discovery of new targets and methods to activate immune function within tumors. However, immunotherapy has been successful so far only subset of metastatic patients. Metastatic melanoma is highly heterogeneous cancer and lack of response to current treatments is largely due to high heterogeneity in the tumor microenvironment (TME) of melanoma. Lactate-rich TME has been shown as highly immunosuppressive and promotes tumor growth and progression. Cancer cells transport lactate across the cell membrane to the extracellular matrix via monocarboxylate transporters, MCT1 and MCT4. We have developed dual MCT1/4 inhibitors (dMCTis) to block lactate excretion to the TME thereby directly killing cancer cells and simultaneously activating local immunity in the TME. In our preliminary studies, we have shown that dMCTis are potent compounds against multiple melanoma cell lines in vitro. Also, we have shown that in in vivo experiments with both xenograft model (MDA-MB-231, breast cancer) and syngeneic mouse models of melanoma; B16-F10 (BRAFWT) and SM1 (BRAFV600E), MCT1/4 inhibitors exert significant anti-tumor efficacy. Anti-tumor efficacy in MDA-MB-231 immune-deficient xenograft model shows inhibitors? direct cell killing effect. In the SM1 syngeneic model, we observed a decrease in expression of multiple immunosuppressive molecules such as B7 family proteins in treated tumors compared to the control tumors. Furthermore, profiling of cytokines indicated an increase in pro-inflammatory IFN?, TNF?, IL-1? and decrease in tumor promoting TGF?, IL-10 in treated tumors compared to the control tumors confirming that the anti-tumor effect of dMCTis is in part due to enhanced immune function. This was further corroborated by the immune only efficacy of the compound in B16-F10 model indicating the immune component of these compounds. Supported by the preliminary data, we hypothesize that blocking the lactate shuttle with MCT inhibitor will reprogram the metabolic landscape of tumor microenvironment in melanoma by suppressing the tumor growth and enhancing the immune surveillance, thereby promoting the efficacy of these inhibitors as a single agent or in combination with immune check point inhibitors in metastatic melanoma. To test our hypothesis, we propose the following specific aims: (1) To study in vitro effects and mechanisms of dMCTi inhibitor, NGY-B in representative melanoma cell lines, (2) To investigate the efficacy and immune activation power of NGY-B in immune-deficient A375 mouse xenograft model, (3) To evaluate in vivo effects of NGY-B as a single agent and in combination with immune checkpoint inhibitors in immune-competent SM1 and B16-F10-metastatic mouse models. The proposed work will determine the feasibility of dMCTis as novel immunotherapeutic agents to treat metastatic melanoma. We anticipate that the proposed study will enhance our understanding of the role of lactate on local TME, and its effect on the composition and function of infiltrating immune cells to develop novel immunotherapeutic combinations to treat metastatic melanoma.